1. FIELD OF THE INVENTION
The present invention relates to laminates for interior finish materials, i.e. laminates to be fitted to the inner walls of the ceiling, door, window frame or trunks of motorcars or to the inner walls of rooms of buildings.
2. DESCRIPTION OF PRIOR ARTS
A frame and a covering material of, for example, the ceiling of motorcar have been adhered to each other with an adhesive of the paint type. Recently, however, because of problems of public nuisance, i.e. environmental pollution and ill effects on the health of human bodies or problems of complicated steps of operation which cause prolonged operation time and poor productivity, investigations have been carried out for developing of a hot melt adhesive which does not require any solvent. The most simple method is to use a film-form hot melt adhesive. Investigations have been made on various hot melt adhesives in the form of films. Vinyl films such as ethylene/vinyl acetate copolymer resin (hereinafter referred to as EVA) and polyolefinic films such as polyethylene (hereinafter referred to as PE) have been examined. However, they were unsuitable for interior finish materials.
One requirement for the quality of interior finish materials for motorcars and buildings is that the material should pass a heat resistance test carried out at a temperature above 80.degree. C. However, if EVA is used, the covering material comes off from the frame at a temperature above 80.degree. C. due to the poor adhesive strength of EVA at such a high temperature. For example, in the case of a ceiling material, the covering material comes off and hangs disadvantageously.
As the covering materials used for interior finish materials, laminates of a buffer material such as foamed polyurethane or foamed polyethylene and a polyvinyl chloride sheet are used mainly. If they are subjected to thermal adhesion at a temperature above 100.degree. C., there are posed problems such as that the covering material is spoiled by the heat. For polyolefin films such as films of said polyethylene, a sufficient adhesive strength cannot be obtained unless a higher adhesion temperature is employed than that of EVA. Consequently, the covering material is spoiled by heat and, further, a long adhesion time (usually 30-50 seconds) is required. In addition, both the workability and productivity thereof were unsatisfactory.
Thus, under the existing circumstances, no hot melt adhesive which is satisfactory with respect to both efficiency and workability has been found yet.
Recently, there has been developed a hot melt adhesive comprising a polyamide copolymer (nylon 6/66/12) of a low melting point containing lauryllactam as indispensable ingredient (for example, Japanese Patent Publication No. 22240/1970 is referred to). There has been developed further a polyamide copolymer of a low melting point comprising four kinds of monomers (for example, Japanese Patent Laid-open Application Nos. 35290/1975, 35291/1975 and 22034/1975 are referred to). However, the lowest melting points of those adhesives are around 100.degree. C., which are substantially equal to the melting point of said polyolefinic hot melt adhesive. From this fact, it cannot be expected that those polyamide copolymers can be used suitably as interior finish materials.
Particularly, the hot melt adhesives of a low melting point containing lauryllactam or .omega.-aminoundecanoic acid as indispensable component are prepared for use as hot melt adhesives for fibers and fabrics. The lower the melting point, the better is the adhesive for fibers and fabrics. It could not be expected that the hot melt adhesives can be used for the adhesion of a frame to a covering material for the interior finish material of motorcars which are used under very severe conditions as in the present invention.